Electrocapacitive properties of supercapacitors based on hierarchical porous carbons from chestnut shell

Three porous carbons CSC-6, CSC-7, and CSC-8 were prepared by the carbonization of zinc chloride-pretreated chestnut shells at 600, 700, and 800 °C under N2 atmosphere and had specific surface areas of 1754, 1987, and 1824 m2 g−1, respectively. The microstructure and surface functional groups of samples CSCs were characterized by thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and Raman spectroscopy. Electrochemical performances of CSCs-based supercapacitors were evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge, self-discharge, cycle stability, and electrochemical impedance spectroscopy (EIS) in two-electrode cells. Comparative studies showed that the CSC-7-based supercapacitor exhibited the best electrochemical performance among all the CSCs-based supercapacitors. At a current density of 0.1 A g−1, the CSCs-based electrodes had the specific capacitances of 42.5, 105.4, and 83.4 F g−1 in 6 M KOH solutions for CSC-6, CSC-7, and CSC-8, respectively. With the current density up to 10 A g−1, the CSC-7-based electrode still showed a capacitance as high as 92.0 F g−1. Based on the experimental results, the relationship between the electrochemical properties of the CSCs-based supercapacitors and structural nature of samples CSCs was analyzed and discussed.